In my experience, bio-based oil well cement retarders do not provide the consistency needed to control thickening time accurately. (This is at least, the case among types of cement used in oil wells). The main reason is that the production of natural organic retarders varies from lot to lot and batch to batch.
The problem with organic retarders
Down-hole conditions, process control and small variations in cement quality; all play a significant part in the inconsistencies of natural organic retarders and other biopolymers used in the industry. Those such as the cellulose derivative, hydroxyethylcellulose, used as a common fluid loss additive in oil well cementing, experience the same pitfalls as other biopolymers within the oil and gas industry.
We can take a look at an organic molecule and a synthetic polymer. These are both used to control thickening time of the cement slurry. We can easily see why it is the much safer and best choice to opt for a synthetic product.
Thickening time, however, also depends on the:
- Job conditions
- The validity of the BHST
- The determination of the BHCT
- The mix water preparation
- Density control
- Plus other operational aspects.
This analysis is the role of the service company. If we take aside the necessary design and operational controls, it is clear that the first step to making consistent and predictable cement slurry is to treat it with synthetic additives.
Encouraging results from a synthetic retarder trial
Recently, I came across a system that claims to provide excellent results. Even more importantly, reproducibility in thickening within a very, very low standard deviation. This is an excellent advantage to lower costs, laboratory time (e.g., equipment usage) and increases the service quality we deliver to our costumers. Well control, zonal isolation and well integrity are all positivity affected. This maximizes well security and operational safety.
This synthetic retarder provides reproducible results, increases safety through additive engineering. This, in turn, offers predictable results based on the system’s designed linearity.
The system offers excellent fluid loss data, thickening time results, rheology, strength retrogression, expandability. It is cost effective and rigid. It has thermal stability and can perform in HPHT conditions (temperatures as high as 450 F), as well as in temperatures as low as 100 F. The linear response makes this state of the art and a safe-to-use oil well cement system.
After probably only a few years in the industry, we all know well that biopolymer-based systems commonly used have entirely too much variance and other side effects. Sure, they work, but there is no real predictability. That can be very difficult for our laboratory guys with obvious implications in service quality.
Here I will introduce a simple truth, we all know:
The more time the slurry spends in the lab, the higher the risk for the well
Risk elevation can be dangerous and costly to operators.
We derive biopolymers in a naturally organic way, and their quality may vary significantly from lot to lot. Variation in quality makes inventory control more difficult for services companies. This is in addition to the issues already mentioned, all with tremendous effect on service quality.
On the contrary, synthetic cement retarders will provide accuracy time after time. This synthetic product, like any other, is man-made, so the reaction environment is controlled, and it does not change. It’s purely linear, so if you want 2hrs, you can treat with 0.02gal/sks. If you want 3 hrs, you can treat with 0.03gal/sks, for instance.
For inquiries about these cement retarders, and how you can obtain samples and brochures, send email to lenin.diaz@better-cementing-for-all.org
Cheers
L. Diaz
Mr. Diaz,
I respectfully disagree that the synthetic retarders are the go to choice. I have not found them to be as predictable as you have suggested (with lab time savings etc.).
Yes, in certain instances they do provide a somewhat linear response, but only in the situation that nothing has changed i.e; the same cement, same additives, and same general well conditions.
Many synthetics in fact, seem to respond in a linear fashion related more pressure as opposed to temperature, which can be very beneficial.
But I have not found them to significantly save lab time until reaching mid-temperature (+/- 165°F BHCT).
The selection of synthetic retarder for higher temperatures can be argued on volume, and effectiveness as well as predictability. Synthetics become more cost/execution effective as the BHCT increases, and the volume of a Biopolymer is significantly increased.
In comparison, I have found Biopolymers can also have sufficient predictability in the right situation, some of them even in the mid to high temp range, at lower pressures, can provide a more competitive choice in both effectiveness and cost, without sacrificing predictability or repeatability.
This all goes back to the theories on the mechanism of action for retarders, and what is going to be the most effective in a given situation. The better we can understand our cement properties, the better our retarder selection will be. Of course, that only comes with lab time… unfortunately.
I like the discussion.
Thanks,
Jeff
Indeed Jeff, this is a good point you are making. I am not trying to simplify things out; designing a cement slurry, even for similar wells, would always have some degree of “uncertainty”. And it has to do with the cement batch, temperaure and other things.
However, It is very interesting you mention the linearity related to pressure and not temperature. Maybe if you have the time, you can tell us a bit more here, that would be great. Thanks
Hello Lenin,
Nice topic. I have observed that the retarders are highly active in a specific temperature range. For synthetic retarders, it is +/- 170 to +/- 250 F. Within this temperature range, the retarder exhibit non-linear performance. This can be observed with the natural retarders as well. Though I agree with you on batch-to-batch variation in performance, there is also a variation within samples of the same batch (perhaps due to the blending process or storage). And such variations would magnify if the additive is liquid and is stored in large containers (of size of tote tanks or larger) and if no proper equipment available on field to homogenize the contents in such tanks. Significant variations can be observed between the tests conducted with the lab samples of retarder and those with the samples from field.
So, with all due respect, if someone claims that the system is giving reproducible results, it is worth checking the conditions. Because, the tests conducted under meticulously controlled environments always produce reproducible results as some of the variation causing parameters are always eliminated under such controlled environment.
Thanks,
Kedar
Thanks Kedar. Well said. Certainly reproducibility, in this context, would depend on a variety of conditions and situations.